The present invention relates generally to line scan cameras, and more particularly to a new and improved internal automatic calibration and built-in diagnostic system for use in conjunction with a line scan camera wherein an optical assembly, comprising a lens component and a charge-coupled device (CCD) subassembly, and an optical bench assembly, which includes an object plane across which objects to be photographed are conveyed, are initially integrated together such that once the optical assembly is calibrated and locked in position with respect to the optical bench assembly by means of factory technicians, further calibration or recalibration of the optical assembly, or more particularly, further calibration or re-calibration of the lens and charge-coupled device (CCD) components, with respect to each other as well as with respect to the optical bench assembly, and more particularly, with respect to the object plane thereof, is no longer required. In this manner, should routine maintenance of the line scan camera be required whereby the optical components of the camera would need to be disassembled and reassembled, recalibration of the optical assembly, with respect to the optical bench assembly, is obviated. In addition to the foregoing, and subsequent to, calibration of the optical assembly with respect to the optical bench assembly, the line scan camera of the present invention further comprises a new and improved internal automatic calibration and built-in diagnostic system wherein the proper framing of the camera image, as well as the proper exposure levels and uniformity of the photographed image across the entire expanse of the photographed image, is able to be achieved and effectively permanently locked into the internal operating systems of the camera such that once the camera is properly internally calibrated, consistent photographic images can always be achieved thereafter.
As disclosed within the aforenoted U.S. patent application Ser. No. 09/810,397, filed on Mar. 19, 2001 in the name of Robert M. Krohn et al., and entitled LOW MAINTENANCE LINE SCAN CAMERA, line scan cameras are used in various industrial or commercial applications, such as, for example, in those instances or circumstances wherein the camera is maintained stationary while the objects to be photographed or scanned are moved with respect to the camera. One such exemplary industrial or commercial application comprises the use of line scan cameras in connection with the high-speed sorting or processing of mail pieces. In accordance with such systems, for example, pieces of mail are conveyed past a point or object plane at which the line scan camera scans or photographs the same. In order to achieve the necessary high-speed scanning or photographing of the mail so as to, in turn, ensure the high-speed processing or sorting of the millions of pieces of mail which enter the mail or postal system on a daily basis, relatively simple, accurate, high-speed, and reliable line scan cameras, devices, or systems are required. In order to achieve such simplicity, accuracy, and reliability in connection with the camera structure, for example, it has been disclosed within the aforenoted patent that the line scan camera has been provided with a positional calibration system whereby once the lens component or assembly has been positionally calibrated with respect to the object plane, as well as with respect to the image or focal plane as defined by means of the charge-coupled device (CCD), additional or further positional recalibration of the lens component or assembly is no longer required.
Accordingly, even if the camera lens and charge-coupled device (CCD) components are removed from their normally fixed or mounted positions defined within the overall line scan camera apparatus, and subsequently replaced or remounted within the overall line scan camera apparatus, in accordance with, for example, the performance of maintenance or repair operations, the original positional locations of the replaced or remounted lens and charge-coupled device (CCD) components of the line scan camera can be ensured by means of the aforenoted calibration systems so as to in fact precisely locate or mount the lens and charge-coupled device (CCD) components at their original positions. In this manner, the need for any additional, subsequent, or supplemental positional calibration by, for example, unskilled field location personnel or technicians, would not in fact be required and would accordingly be obviated. In a similar manner, subsequent to the implementation of the aforenoted positional calibrations being performed by skilled manufacturing personnel or technicians in connection with the various structural components of the camera, that is, once the mounting of the various optical components upon the optical bench assembly has been completed, additional calibrations need to be performed in the field in connection with the internal operational functions or processes of the camera in order to additionally ensure that the actual photographs or images, subsequently taken or captured by means of the camera, will exhibit, for example, the desired image framing, the proper exposure parameters or characteristics, a proper or desired degree of uniformity within and throughout the field of view comprising the image, and the like.
More particularly, for example, it is critically important to accurately determine or properly frame the image field of view, comprising, for example, the true locations of the bottom and leading edges of the article being scanned or photographed such that portions of the captured image, characteristic of the individual articles being scanned or photographed, are not inadvertently cut off or undesirably curtailed. Still further, it is likewise critically important to ensure that the resulting image perceived or captured by means of the line scan camera exhibits substantial uniformity throughout the entire extent thereof such that all regions of the resulting image in fact exhibit high quality contrast, resolution, brightness, and other similarly desirable characteristics.
A need therefore exists in the art for new and improved built-in diagnostic procedures and automatic calibration adjustment or correction techniques for use in conjunction with line scan cameras wherein proper image framing and image characteristics can be automatically achieved, and wherein further, the calibration adjustments or correction factors can be effectively permanently locked into or stored within the line scan camera software whereby once such diagnostic procedures and automatic calibration adjustments or corrections have been performed and achieved, all imaging subsequently performed by means of the line scan camera will exhibit the desired framing and image characteristics.
Accordingly, it is an object of the present invention to provide a new and improved line scan camera having automatic diagnostics, and calibration procedures and techniques, incorporated therein.
Another object of the present invention is to provide a new and improved line scan camera having automatic diagnostics, and calibration procedures and techniques, incorporated therein so as to effectively overcome the various operational deficiencies characteristic of conventional PRIOR ART line scan cameras.
An additional object of the present invention is to provide a new and improved line scan camera having automatic diagnostics, and calibration procedures and techniques, incorporated therein wherein proper image framing is able to be automatically achieved such that portions of the captured image, characteristic of the individual articles being scanned or photographed, are not inadvertently cut off or undesirably curtailed.
A further object of the present invention is to provide a new and improved line scan camera having automatic diagnostics, and calibration procedures and techniques, incorporated therein wherein uniformity and maximization of exposure levels are able to be achieved throughout the entire extent of the captured image.
A last object of the present invention is to provide a new and improved line scan camera having automatic diagnostics, and calibration procedures and techniques, incorporated therein wherein uniformity and maximization of exposure levels are able to be achieved throughout the entire extent of the captured image by means of suitable calibration adjustments and correction factors, and wherein further, the calibration adjustments or correction factors can be effectively permanently locked into or stored within the line scan camera software whereby once such diagnostic procedures and automatic calibration adjustments or corrections have been performed and achieved, all imaging subsequently performed by means of the line scan camera will exhibit the desired framing and image characteristics.
The foregoing and other objectives are achieved in accordance with the teachings and principles of the present invention through the provision of a new and improved line scan camera, which comprises automatic diagnostics, and calibration procedures and techniques, incorporated therein, wherein in order to achieve the proper framing of the image field of view, a first test card is employed in order to properly determine the true bottom and leading edge portions of an article being scanned or photographed. The first test card comprises at least one horizontally oriented black line and at least one vertically oriented black line in connection with which the true bottom and leading edge portions of the test card, which simulate the true bottom and leading portions of an article being scanned or photographed, can be determined. More particularly, in connection with the determination of the true bottom edge portion of the first test card, and those of the articles being scanned or photographed, software integrated within the line scan camera is already pre-programmed so as to reflect the fact that the entire vertical extent or expanse of the photographic or image field, as effectively seen or defined within or upon the charge-coupled device (CCD) of the line scan camera, comprises a predetermined number of pixels as serially numbered vertically upwardly from the bottom of the image field to the top of the image field. In addition, the horizontally oriented black line is located a predetermined distance dimension above the bottom edge portion of the calibration card, and the software integrated within the line scan camera is also pre-programmed so as to effectively convert such predetermined distance dimension into a corresponding number of pixels. Therefore, the disposition or location of the bottom edge portion of the calibration card can be readily determined, as can the leading edge portion of the calibration card as a result of similar calibration techniques with respect to the vertically oriented black line of the calibration card.
Still further, the architecture or inherent structure of the electronic chip incorporated within the charge coupled device (CCD) effectively divides the linear array of pixels into four channels, and in order to achieve uniform exposure levels throughout the entire linear array of pixels comprising the line scan of the camera, amplifier gain and black offset adjustments or calibrations are made with respect to the exposure levels characteristic of the pixels disposed at the channel boundaries, under different degrees of input whiteness signals, so as to achieve channel-to-channel seam matching. Subsequently, correction factors are effectively superimposed upon substantially all of the exposure levels characteristic of substantially all of the pixels comprising the line scan of the line scan camera such that true uniform exposure levels are in fact achieved.